The huge pipes with which feedwater is conducted to steam generators heated by nuclear fission, are beginning to evidence progressive defects. This problem is only one of the myriad of other technical problems descending upon these installations. Fortunately, consistent improvement in inspection apparatus and techniques have given early warnings by spotting the appearance of internal cracks in the walls of these feedwater pipes. Forewarned, the maintenance personnel rise to the occasion by developing tools and techniques to catch these defects in their early stages of development and overcome them.
Thus far, the internal cracks of these feedwater pipes have appeared only in straight runs. But the location, size, and expense of replacement of straight-run sections make it advisable to directly attack the developing defects in situ. Some of the internal cracks can be ground out and leave enough wall thickness for safety. Other cracks are ground out and the depression filled with weld material which is to be ground flush with the internal pipe surface.
Superficially, it would appear that personnel could crawl inside of these rather large pipes and apply a hand-held grinding machine to the cracks. Large as the pipes are, perhaps in the order of 17-18", they remain a limited boundary within which it is difficult, or impossible, to operate hand-held grinding machines effectively. Adjustable support structure for the grinding machine must be provided. Within the boundary of the pipes, personnel can insert and install support apparatus for the grinding machine. The actual radial adjustment of the grinding machine from the axis of the pipe to the predetermined station on the internal wall, and axial movement as required, must be carried out by manual operation of the support structure. Within these specifications, the present invention provides a tool which obviates still another problem in nuclear power generation.